CONCHIFERA. 571 



possess any, may be situated in the filaments of the mantle- 

 margin, and those of touch, doubtless, consist of the curiously- 

 twisted cirrhated arms or labial appendages. The Brachio- 

 pods appear to be altogether destitute of true gills, the 

 function of respiration being performed by the vascular 

 mantle, which is furnished for the purpose with numerous 

 large, ramifying veins. Their digestive organs do not 

 differ materially from those of the Bivalves, the alimentary 

 canal commencing in a simple oral aperture situated between 

 the bases of the contorted arms ; in Terebratula it is tubu- 

 lar and curved for some distance, and then becomes dilated 

 into a stomach, while in other genera it makes several 

 turns, and continues throughout of the same calibre ; there 

 are no salivary glands, and the disintegrated liver pours its 

 secretion directly into the digestive tube. 



The mode in which the Brachiopod Mollusks are attached 

 to foreign bodies varies in each family ; the regular and 

 deep-dwelling Terehratulidte are anchored to sub-mariue 

 bodies by a tendinous peduncle which escapes through the 

 perforated beak of the ventral valve which is also the upper 

 valve, as these animals, like the Cirrhopods, repose upon 

 their backs ; in the horny, flattened Discinidce the tendon 

 of attachment passes through a fissure near the hind part of 

 the under valve ; in the singular Lingtilida, which perforate 

 the mud of shallow bays, the peduncle is tubular, and es- 

 capes from between the diverging beaks ; the Cramida, 

 which are sessile on stones and other submarine bodies, are 

 directly attached by their flattened lower valve ; while the 

 Thecideidce, which have the perforation in the beak rudi- 

 mentary or closed, are fixed by the apex only of the lower 

 valve. 



The bodies of the Brachiopods are protected by two un- 



